A guy on DT just put SRT8 Kooks headers on a 2wd truck with only a slight tap on a primary to make it fit! OBX ones should work fine...might need a little TLC on one primary tube, but easy install!

Here is a copy and paste to the post Timmy is talking about. This guy installed Kooks SRT8 longtubes and he also said that OBX longtubes will fit. His truck is a 2011 2wd express. He is running a '10 PCM swap with the rear O2s turned off to avoid the typical codes associated with a longtube install.

"Installed a set of Kooks On my 2011 Ram last Night...
They are Off a SRT8 Jeep.
Got them Pretty cheap used.
I didnt have to do any modification on the passenger side for fitment except remove a heat shield that coverts the rear of the motor mount.
On the drivers side i had to remove the same shield and dent one of the primary tubes about an 1/8th inch to clear the motor mount.

Well worth it IMO
The small dent will not affect performance at all.

*Note*
You will need a longer O2 sensor on the drivers side.
On passenger side you will need to cut the zip tie holding the sensor up so it can reach the header"